Method and apparatus for detecting defects using digital radiography

Abstract

A digital radiography apparatus ( 10 ) and process for providing images of an object, for example, an exhaust transition duct ( 12 ) comprising a core material and an overlying thermal barrier layer, to detect surface and interior defects within the duct ( 12 ). Incident energy is provided by an energy source ( 30 ), transmitted through the object ( 12 ), and sensed by a sensor ( 32 ). An image of the object ( 12 ) is formed by processing the signal from the sensor ( 32 ) in a signal processor ( 34 ) and displaying the image on a display ( 36 ) for determining defects in the object ( 12 ).

1. A method for detecting internal features of an object, wherein the object comprises a metallic core material and a thermal barrier layer that prevents visual inspection of the core material, the method comprising:
 subjecting the object to incident energy;  
 sensing the energy transmitted through the object;  
 converting the sensed energy into representative digital data;  
 processing the digital data to form an image of the object, wherein the image is characterized by image parameters;  
 positioning the object relative to the incident energy to image regions of the object; and  
 controlling the image parameters to remove the effects of the thermal barrier layer.  
 
     
     
       2. The method of  claim 1  wherein the incident energy is selected from among light, heat, sound, transmissive ultrasound, electromagnetic radiation, x-rays, gamma rays, and sub-atomic particles further comprising electrons, protons, neutrons and heavy ions. 
     
     
       3. The method of  claim 1  wherein the incident energy is defined by a plurality of exposure parameters, further comprising adjusting one or more of the plurality of exposure parameters. 
     
     
       4. The method of  claim 3  wherein the plurality of exposure parameters comprise exposure duration, incident energy frequency, and incident energy intensity. 
     
     
       5. The method of  claim 3  further comprising acquiring multiple images of a region of the object, wherein the step of adjusting is executed between acquiring successive multiple images of the region. 
     
     
       6. The method of  claim 3  wherein each of the regions is associated with a predetermined set of exposure parameters. 
     
     
       7. The method of  claim 1  wherein the step of controlling the image parameters further comprises removing the effects of the thermal barrier coating to analyze features of an interior of the core material. 
     
     
       8. The method of  claim 1  wherein the step of controlling the image parameters further comprises removing the effects of the thermal barrier coating to analyze features on a surface of the core material. 
     
     
       9. The method of  claim 1  wherein the step of controlling the image parameters further comprises enhancing the visibility of internal features. 
     
     
       10. The method of  claim 1  further comprising analyzing the digital data to detect an anomaly in the core material. 
     
     
       11. The method of  claim 10  wherein the anomaly is declared to indicate a defect if the size of the anomaly is greater than a predetermined value. 
     
     
       12. The method of  claim 10  wherein the anomaly is declared to indicate a defect if the number of anomalies within a defined region of the object is greater than a predetermined number. 
     
     
       13. The method of  claim 10  wherein the anomaly is declared to indicate a defect if the anomaly is within a predetermined distance of a defined region of the object. 
     
     
       14. The method of  claim 1  wherein the object has a non-uniform thickness. 
     
     
       15. The method of  claim 1  wherein the parameters of the incident energy are varied to permit analysis of an interior of the core material. 
     
     
       16. The method of  claim 1  further comprising displaying the image. 
     
     
       17. The method of  claim 1  further comprising repeating the step of positioning the object such that the digital data represents substantially the entire object. 
     
     
       18. An apparatus for detecting internal features of an object, wherein the object comprises a metallic core and a thermal barrier that prevents visual inspection of the core, the apparatus comprising:
 an energy source for transmitting incident energy toward the object;  
 a sensor for sensing the energy transmitted through the object;  
 a signal processor for converting the sensed energy into representative digital data and for processing the digital data to form an image of the object, wherein the image is characterized by image parameters;  
 a holding fixture for positioning the object relative to the incident energy; and  
 wherein the signal processor controls the image parameters to remove the effects of the thermal barrier.  
 
     
     
       19. The apparatus of  claim 18  further comprising a storage device for storing the digital data. 
     
     
       20. The apparatus of  claim 18  further comprising a user-operated input device, wherein the signal processor is responsive to the input device for controlling the image parameters. 
     
     
       21. The apparatus of  claim 18  further comprising a motion controller, wherein the holding fixture is responsive to the motion controller for positioning the object relative to the incident energy to image regions of the object.